Menu editor: moving an application to a new category also pastes it into the category it had been copied from

• Cinnamon version: 4.8.6 (No PPA)
• Distribution: Linux Mint 20.1
• Graphics hardware: Nvidia GM204 [GeForce GTX 970]
• Graphics driver: Nvidia v460.80
• Attach ~/.xsession-errors

Context

Trying to move a badly placed application from one category to another

Issue

• When using the "cut' and "paste" buttons to move an application from one category to another, the application still appears in the category it was previously found in.

  Because of #10139, deleting the application from the older category would make it disappear forever. You need to uncheck it from there

• When using the "copy' and "paste" buttons to copy an application into a new category, the application gets duplicated, now appearing once in the new category and twice in the category it had been copied from.

Expected behavior

• When using "cut" and "paste" to move an application from one category to another, the application should actually be deleted from the previous category

• When using "copy" and "paste" to copy an application into a new category, the application should not get duplicated

Additional info

Originally found while trying to move the "Freetube" Flatpak app from the "accessories" to the "internet" category.

Start by reproducing the issue in Cinnamon's menu editor using the cut/paste and copy/paste actions described, with an application moved between categories. Compare the resulting category entries with the expected behavior: cut/paste should remove the old entry, while copy/paste should add only one entry in the destination and not duplicate the source entry.